Cold working of metals affects the mechanical properties of those metals. These effects are particularly important in the design, analysis and subsequent performance of materials used in elevated temperature nuclear construction. This paper provides an assessment of the effects of cold working on the time independent and time dependent mechanical properties of the materials most commonly encountered in liquid metal fast breeder reactors. The paper suggests specific reductions, as a function of time, temperature and cold work level, for those properties adversely affected. The final objective of this paper is to provide an assessment of the manner in which the Code now addresses fabrication effects and how it might make those assessments in the future.